We have demonstrated the synthesis of the 32,000 mw common precursor for ACTH-endorphin in intact toad and mouse intermediate lobes, and have studied its conversion to the final peptide products in vivo and in vitro. These studies have revealed that glycosylation of the prohormone plays a regulatory role in its conversion, and that the toad lobe has two independently regulated and distinct pools of hormones and precursors. A converting-enzyme for the prohormone has been detected in secretory granules and characterized.